Reciprocating motor core structure



vMaalrch 26,- 1968 v DHU AINE J; DAvls 3,375,380

RECIPROCATING MOTOR CORE STRUCTURE Filed Feb. 10, 1967 f; ATTORNEYS United States Patent ABSTRACT OF THE DISCLOSURE This invention relates generally to an electric vibratory tool and particularly to improvements in electrically operated etching tools.

Background of the invention Electric etching tools generally include an electromagnetic motor mounted within a casing and having a core and coil and a movable armature which reciprocates an etching nod for the purpose of marking or engraving on hard surfaces such as metal or plastic. The etching tools heretofore available include a relatively large and bulky casing within which the electromagnet is mounted. This bulkiness results from employing a standard, somewhat reetangularly shaped, coil and core. Such structures are cumbersome and diiiicult to handle and use. They in no way resemble the elongate writing instruments with which most people are familiar. Furthermore, the operating mechanism within the tools casing is made of numerous relatively detailed parts and thus the tool is much too expensive for general use.

Summary of the invention i One object of this invention is the provision of a novel elongate etching tool having a coil, core and armature structure so constructed that the etching tool as a whole simulates a pencil or other elongate writing instrument.

Another feature of the invention is the provision of an etching tool of the character described which includes a readily accessible means for adjusting the mechanical displacement of the etching rod.

Still another feature is the provision of a single nose piece within the casing to guide the etching rod, to guide the armature member and prevent it from binding, and to position the spring means which biases the armature away from the electromagnet.

It is yet a further object of this invention to provide a tool which includes a two piece hinged core which permits easy manufacture and assembly of the tool.

Still a further feature is the provision of such a tool having an elongated coil and core configuration with an armature at one end of the core, permitting the tool to be formed with a very slender shape.

Other features and objects of this invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

Description of the drawings Detailed description Turning now to the drawings, an etching tool embody-n ing the invention has a casing C which houses the component parts of the tool and which is comprised of two matching casing halves and 11. An electromagnetic motor, generally designated 14, is positioned in a cavity (SFIG. 4) within the casing. The casing has an opening 16 in one end thereof and through which an etching rod 13 extends. Terminal leads 20 extend through the casing from the electromagnetic motor at a point remote from the etching rod, preferably at the opposite end of the tool. As can be seen from the drawings, the casing is elongate and has wall means which deline a slender tool simulating a pencil or other writing instrument and which is easily handled by the user. The front portion 22 of the casing tapers toward opening 16 to facilitate easy grasping and manipulation by the user. The etching rod 18 has a pointed tip 24, preferably of carbide or other hard material, and is reciprocated by the electromagnetic motor to permit markings to be etched by the tip on a hard surface such as metal or plastic. The casing is constructed so that the electromagnet is disposed within the cavity 15 beneath a grasping portion 25 (FIG. l) of the casing.

The A.C. electromagnetic motor 14 includes an elongate oval coil 26, a two piece core comprised of two like, elongate, generally rectangular members 28 pivotally secured together at adjacent ends 28a by a combination, nose piece and hinge member 30, and an armature member 32. The motor is mounted in the casing with the armature at the forward end of cavity 15 for vibratory movement toward and away from the elongate electromagnet in the direction of arrow A (FIG. 4). The core members each have a pole face 33 at its forward end. The coil and core of the electromagnet are elongated in the same direction as the casing C. The etching rod 18 is fixed to the armature member 32. A coil Spring 34 embraces the inner end of the etching rod within the casing and is disposed between the nose piece and the armature 32 to bias the armature 32 and etching rod 18 away from the core of the electromagnet. As the current alternates in the coil of the electromagnet, the armature and etching rod reciprocate against spring 32 toward and away from pole faces 33. The armature 32 being at the forward end of the cavity rather than within the coil and/ or core permits the casing to be slender, simulating a pencil.

The nose piece 30 performs four functions in the embodiment of the tool illustrated in the drawings. Its parallel walls 36 serve to guide the armature member 32 and prevent its twisting or binding during oscillation toward and away from the core. The nose piece is provided with a bushing 38 which performs the dual role of maintaining the position of coil spring 34 while guiding the etching rod 18 in its oscillation toward and away from the electromagnetic core. In addition, the single nose piece provides the hinge means for the two piece core to provide for easy assembly of the electromagnet, as hereinafter described.

A means is provided for adjusting the mechanical displacement of the etching rod 18 and includes a coil spring 40 embracing the etching rod 18 within the casing forwardly of the armature member 32. A portion of the opening 16 is threaded to receive a threaded adjusting collar 42 which bears against the outer end of coil spring 40 within the casing by means of a, washer 43. A portion of the collar 42 at its outer end is exposed exteriorly of the casing for grasping and turning by the user to adjust the compression of coil springs 40 and 34. The amount of compression of spring 40 governs the cuter limit of movement of armature 32 and etching rod 18 as they are biased outwardly by spring 34. Thus a simple means at the forward end of the tool is available for adjusting the displacement of the etching rod and thus the depth of the etching on the hard surface.

A ring 44 is threaded onto the front of the tapered easing portion 22 to secure the front of the casing halves together. A boss 45 is formed integrally with the rear of the casing half 10 within cavity 15 and frictionally fits into a socket 46 on the casing half 11 within cavity 15 to secure the rear of the casing halves together.

Referring to FIG. 3, each elongate core piece 28 is a stack of laminatons; and the elongate coil 26 is disposed between the two core pieces. The stacks of laminations include 'wider central laminations 47 which extend into the aperture of coil 26. In the embodiment illustrated, both core pieces 28 include wider central laminations 47 which extend half way through the coil 26. The core may be formed with only one core piece 28 having wider central laminations which extend all the way through the coil. The cross-sectional area of the central laminations are of the same order as the area of the pole faces 33. The ease of assembly of this construction is readily apparent. The laminated core pieces 28 and nose piece or hinge member 30 may easily be assembled independently of coil 26. Then, by spreading the two core pieces apart, the coil may be positioned therebetween and .the core pieces closed on the coil. The core and coil assembly does not employ screw or other `fastening means to hold it together or to mount it in the casing. The single nose piece 30 positions coil spring 34, guides etching rod 18 and prevents armature member 32 from binding. Since the adjusting collar 42 is threaded directly into the casing C, the entire structure is assembled into the casing without a single screw or fastening means. Once the component parts are assembled in the casing, the only fastening means necessary is to secure the two casing halves 10 and 11 together. This is accomplished by ring 44 and a friction t between boss 45 and socket 46.

Another important feature of the invention is that each core member 28 is tapered with its minimum cross-sectional area at its end 48 remote from the core faces 33 (except for the enlargements 49 which receive rivets 50). Such a configuration concentrates the magnetic field toward the front of the core members 28 at their pole faces 33 to provide the maximum effective magnetic field for the size of the coil. This configuration also moves the center of gravity of the core toward the front of the tool where it is grasped to facilitate easier handling; and minimizes the amount of iron used in the core, reducing weight and cost.

It can be seen that the positioning of the core and coil within the grasping portion of the casing, the positioning ofthe armature at the front of cavity 15, and the tapered conguration of the core members 28 all cooperate to provide a slender, well balanced and powerful tool while facilitating the use of a relatively small elongated coil 26.

While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and is herein described in detail one embodiment of the invention, with the understanding that the present disclosure is to be considered as an exemplication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims.

I claim:

1. An electromagnetic motor for a reciprocating tool comprising: a coil with an axis, said coil having an oval configuration in a plane at right angles to `said axis; a pair of elongated magnetic core members extending transversely to said coil axis and Igenerally parallel with the major axis of the oval coil, each of said core membersl having an end forming a pole face and an end remote therefrom, the cross-sectional area of the core members being greater at the pole faces than at points between the ends; and a magnetic armature operably associated 'with 4said pole faces.

2. The electromagnetic motor of claim 1 wherein each of `said core members is tapered, having a minimum crosssection at the ends thereof remote from said pole faces.

3. An electromagnetic motor for a reciprocating tool, comprising: a coil with an axis, said coil having an oval configuration in a plane at right angles to said axis and having an oval aperture therethrough; a pair of magnetic core members extending transversely to said coil axis and generally parallel with the major axis of the oval coil,

each of said core members having an end forming a pole face and a core portion extending between the core members through the aperture, the cross-sectional area of said core portion being of the same order as the area of each of said pole faces; and a magnetic armature operably associated with said pole faces.

References Cited UNITED STATES PATENTS 2,196,667 4/ 1940 Moseley 310-29 XR 2,25 9, 1 3 1 10/ 1941 Fleischer et al 310-29 2,278,365 3/ 1942 Daniels 310-29 3,113,226 12/1963 Moret 310-38 DAVID X. SLINEY, Primary Examiner.

D, F. DUGGAN, Assistant Examiner. 

